This invention is related to a method of making a modified silica filler in which silica is contacted with a blend or mixture of (i) a dialkyldichlorosilane and (ii) a trialkoxysilane free of groups reactive with a silica surface, in a weight ratio of 1:0.1 to 1:2, respectively.
This is an improvement in methods of modifying silica fillers as described in, for example, U.S. Pat. No. 6,384,125 (May 7, 2002) assigned to the same assignee as the present invention. While the ""125 patent refers generally to the use of some similar organometallic compounds and mixtures thereof as the present invention, and their use as hydrophobing agents for silica, it does not describe any particular mixture or blend of organosilicon compounds as being any more effective than any other blend, nor does the ""125 patent teach that a particular ratio of organosilicon compounds is necessary to achieve new and unexpected results, i.e., the ability to deposit more siloxane on silica, vis a viz, improved hydrophobicity.
In addition, the ""125 patent fails to teach using only dialkyldichlorosilanes and trialkoxysilanes free of groups reactive with silica surfaces. Rather, the ""125 patent requires a second component referred to as a functionalizing coupling agent containing groups such as vinyl, allyl, hexenyl, epoxy, glycidoxy, and (meth)acryloxy.
The invention is directed to a method of making modified silica fillers in which silica is contacted with a blend or mixture of organosilicon compounds. In particular, the invention is an improvement and consists of treating silica surfaces with compositions in which the organosilicon compounds in the compositions are only of types of structural groups of monomeric dichlorosilanes and trialkoxysilanes. The organosilicon compounds in the compositions may be mixtures and blends of substituted or unsubstituted dialkyldichlorosilanes, and trialkoxysilanes free of groups reactive with silica surfaces. The mixtures and blends contain (i) a dialkyldichlorosilane and (ii) a trialkoxysilane free of groups reactive with a silica surface, in a weight ratio of 1:0.1 to 1:2, respectively. Preferably, the weight ratio is 1:0.3 to 1:1, and most preferably the weight ratio is 1:0.5.
These and other features of the invention will become apparent from a consideration of the detailed description.